1. Field of the Invention
The present invention is concerned with a greatly improved cellular drift eliminator especially designed for use in connection with counterflow water cooling towers wherein descending quantities of hot water are brought into intersecting, thermal interchange with upflowing currents of ambient-derived air. More particularly, it is concerned with such a drift eliminator which serves to remove a significant portion of entrained water particles in the air leaving the tower fill, while at the same time avoiding undue pressure drops. In addition, the eliminator hereof produces a size distribution in water particles leaving the tower which is desirable, i.e., a large proportion of entrained water particles leaving the tower are of relatively small size so that excessive wetting of equipment and structures closely adjacent the tower is avoided.
2. Description of the Prior Art
In evaporative water cooling towers of the counterflow variety heat is removed from initially hot water by causing the latter to gravitate through a surface-increasing fill assembly in counterflowing, intersecting relationship to currents of cool, ambient-directed air directed upwardly through the fill. Drift eliminators are normally provided to remove entrained droplets or particles of water from the air leaving the tower fill structure. If drift eliminators are not employed in such a context, substantial quantities of water can be discharged to the atmosphere. This results in undesirable operating conditions leading to excessive wetting of surrounding areas and corresponding coating thereof with mineral deposits. In addition, icing of adjacent equipment and structures can readily occur during wintertime operations. Thus, adequate drift elimination is very necessary with evaporative type cooling towers, especially when large towers are used in metropolitan areas or as a part of a large industrial complex where cold weather occurs.
Although it is desirable from a theoretical standpoint to remove essentially all water particles from cooling tower discharge air, as a practical matter this is an impossibility. Given this constraint, it is important that the particle size distribution of discharged water droplets be the most desirable from the standpoint of avoiding excessive wetting closely adjacent the tower. If, for example, the entrained water particles are relatively large and hence massive, they will tend to deposit on equipment or structures close to the tower. On the other hand, if the entrained particles are of relatively small size, there is a greater tendency for the water to spread and diffuse over a much larger area. In the latter case, undue icing or damage to adjacent equipment or the like is avoided. Therefore, it is important not only to remove as much water as possible on an absolute basis from fill-derived air, but also to ensure that the water which does escape to the atmosphere be predominantly of small particle size.
U.S. Pat. No. 4,040,824 describes a dual path drift eliminator structure which is particularly designed for crossflow cooling towers. The drift eliminator described in this patent includes side-by-side cellular drift eliminator sections separated by an elongated, upright channel or spacing which permits water to drain vertically from the eliminator.
While the two-pass eliminator of U.S. Pat. No. 4,040,824 represents a real advance in the art, particularly in connection with crossflow type cooling towers, attempted use thereof in conjunction with counterflow towers has led to problems. Specifically, the gap or discontinuity established between the cellular air paths tends to provide a region where water particles can coalesce and become reentrained in air passing through the eliminator. This not only lessens on an absolute basis the amount of water removed, but also tends to discharge to the air undesirable, relatively large water particles.
Accordingly, there is a need for an improved cellular-type drift eliminator especially designed for use in counterflow towers and which avoids the problems of excessive amounts of water being discharged from a counterflow tower, and particularly water in the form of large particles.